Advancements in communication technologies have permitted the introduction, and popularization, of new types of communication systems. In various of such new types of communication systems, the rate of data transmission and the corresponding amount of data permitted to be communicated, has increased relative to existing types of communication systems.
New types of radio communication systems are exemplary of communication systems made possible as a result of advancements in communication technologies. Communication channels of a radio communication system are formed upon radio-links, thereby obviating the need for conventional wireline connections between sending and receiving stations operable therein. A radio communication system, therefore, inherently permits increased communication mobility in contrast to conventional wireline systems.
Bandwidth limitations sometimes limit the communication capacity of the communication system. That is to say, the bandwidth capacity of the communication channel, or channels, available to a communication system to communicate information between sending and receiving stations is sometimes limited. And, the limited capacity of the communication channel, or channels, limits increase of the communication capacity of the communication system. The communication capacity of the radio communication system is particularly susceptible to capacity limitation resulting from communication channel bandwidth limitations. Generally, a radio communication system is allocated a limited portion of the electromagnetic spectrum upon which to define communication channels. Communication capacity increase of a radio communication system is, therefore, sometimes limited by such allocation. Increase of the communication capacity of the radio communication system, therefore, is sometimes only possible if the efficiency by which the allocated spectrum is used is increased.
Digital communication techniques provide a manner by which the bandwidth efficiency of communications in the communication system may be increased. Because of the particular need in a radio communication system to efficiently utilize the spectrum allocated in such a system, the use of digital communication techniques is particularly advantageously implemented therein.
When digital communication techniques are used, information which is to be communicated is digitized. In one technique, the digitized information is formatted into packets, and the packets are communicated to effectuate the communication. Individual ones, or groups, of the packets of data can be communicated at discrete intervals, and, once communicated, concatenated together to recreate the informational content contained therein.
Because packets of data can be communicated at the discrete intervals, a communication channel need not be dedicated solely for the communication of packet data generated by one sending station to one receiving station as conventionally required in circuit-switched communications. Instead, a single channel can be shared amongst a plurality of different sending and receiving station-pairs. Because a single channel can be utilized to effectuate communications by the plurality of pairs of communication stations, improved communication capacity is possible.
Packet data communications are effectuated, for instance, in conventional LANs (Local Area Networks). Wireless networks, operable in manners analogous to wired LANs, have also been developed and are utilized to communicate packets of data over a radio-link, thereby to effectuate communications between a sending and a receiving station.
For example, an IEEE (Institute of Electrical and Electronic Engineers) 802.11 standard defines a system for operation of a wireless LAN. Three physical layers are defined in the 802.11, the 802.11a, and the 802.11b standards. The physical layers defined in the 802.11a standard already exist and form the 5 GHz 802.11 standard.
Proposals have been set forth to utilize an unlicensed band located at 5 GHz, also to implement a WLAN operable generally pursuant to the IEEE 802.11 standard. While 5 GHz band is unlicensed, at least in Europe, compliance with certain regulations must be met when communicating in the 5 GHz band. Such regulations include adherence to allowable electromagnetic emissions. A communication system operable at the 5 GHz band must be capable of dynamic adaptation to local interference conditions. Also, systems operable at the 5 GHz band must generate electromagnetic energy emissions which are spread over available frequency channels defined therein. The requirement is a statistical requirement that must be satisfied on a large scale rather than that of a single system. For instance, in systems operable in the 5,470-5,725 MHz range, electromagnetic emissions must be spread across a minimum of 255 MHz.
The IEEE 802.11 standard does not provide for dynamic frequency selection which would facilitate compliance with the electromagnetic emissions spreading regulations.
If a manner could be provided by which to adapt the IEEE 802.11 standard to facilitate frequency allocation upon which to communicate data during operation of a communication system to achieve emission spreading, a communication system operable pursuant to-such standard could be used in the 5 GHz frequency band.
It is in light of this background information related to the communication of data in a radio communication system that the significant improvements of the present invention have evolved.